This invention relates to an optical information recording medium suitable for recording by laser, which is improved in light stability and durability for reading for many times.
Heretofore, there is known an optical information recording and regenerating apparatus which carries out recording and regenerating information by irradiating laser light to a rotating disk-like information recording medium. It is known that an optical information recording medium used in this conventional optical information recording and regenerating apparatus comprises a substrate, metallic reflection film and semi-transparent colored layer containing coloring matter. This recording medium is prepared in such a manner as to satisfactorily detect reflection light reflected from the metallic reflection film when laser light is irradiated through the semi-transparent colored layer containing coloring matter and reaches to the metallic reflection film. This metallic reflection film is provided to supply reflection light amount since an amount of light obtained by the colored layer only is insufficient.
However, the presence of the metallic reflection film makes the structure of an optical information medium complicated and leads to a high production cost. Accordingly, it is proposed to remove the above defect by using a single layer film comprising an organic coloring matter only having a highly reflective bronze gloss. For example, Japanese Patent Laid Open No. 58-112790 discloses that a light absorbing reflection film suitable for recording and reflection regenerating by laser can be obtained by using a cyanine coloring matter of large light absorbing properties as a recording layer, which has a film thickness of 300 .ANG..degree.-600 .ANG..degree. and a metallic gloss (reflectivity=20-30%); and also that there is a merit that an apparatus can be made a small size by using a semi-conductor laser of 750-850 nm as a laser light source. However, this organic coloring matter generally has disadvantages that it is unstable to light and heat and that its preservation stability is poor since it is easily oxidized. Thus, a satisfactory organic thin film suitable for a recording layer has not been developed up to now.